Improvement in valve-gears of steam-engines



UNITED STATES PATENT OFFICE.

JOHN F. ALLEN, OF NEW YORK, N. Y.

IMPROVEMENT lN VALVE-GEARS OF STEAM-ENGINES.

Specification forming part of Letters Patent No. 36,695, dated October 21, 1869.

the following is a full and exact description thereof, reference being had to the accompanying drawings, making part of this speciiication, and to the letters of reference marked thereon.

My invention relates to an'improvement in the means of moving the valves in that class of steam-engines in which the steam and exhaust ports are opened and closed by separate valves which slide upon their seats in operating. In these engines it is the usual practice to effect the alternateopening and closing of the ports at opposite ends of the cylinder by connecting the valves rigidly together, so

that when one is moved to open the port the other is forced to move with it to the same extent.

An improvement on this mode of operating slide-valves was patented by George H. Corliss. In his improvement the valves are still operated in pairs. The two steam or induction valves, for example, are connected by their rods to two wrist-pins on one wrist-plate, which wrist-plate is secured to a rock-shaft, to which a vibrating motion isimparted by an eccentric, through theintervention of an eccentrierod and an arm secured to the rockshaft. Theadvantage gained by this arrangement is quite limited. The arm to which the eccentric-rod is attached must vibrate in ord er to impartsimilar movements to each valve in such an arc that the radius by which it is bisected shall be'perpendicular to a line connecting the point of bisection with the center ofthe shaft carrying the eccentric. rlhe valves,'

therefore, are not moved independently of each other, but the motion given to each is modified in an important degree by the necessity of giving also a similar motion to the other from the vibration of the same arm, rock-shaft, and

Wrist-plate.

. ered, and at the same time to give to them a motion, while the ports are open, more rapid than would beiinparted to them by the eccentric-rod directly; and it is a further object of my invention to effect each of these results in combination, and in a much higher degree than has hitherto been attained, and also to p effect them in nearly the same degree, whatever the throw of the eccentric may be, and at whatever point in the stroke the steam may be cut oft.

To these ends my said invention cons-ists in the employment of an eccentric-rod which at a short distance from the eccentric is divided into two rods, which are attached, respectively, to arms secured to separate rock-shafts, by the vibration of which said rock-shafts motion is communicated, through other arms and rods, to separate valves for admitting the steam or for releasing it, or for'both purposes, at opposite ends of the cylinder. The two arms on either rockshaft may be secured in any desired positions relatively toeach otherand in this manner each may be caused to vibrate through any portion of a circle, whereby, employing the familiar principle of the toggle-joint, Inotion in either direction, and either more slow or more rapid than that of the eccentric-rods, in a right line, and this in almost any desired degree, can be imparted to the valve or valves which are operated by one rook-shaft, without being in any manner affected by the similar motion to be given to the `valve or valves which are operated by the other rock-shaft.

To enable others skilled in the art to make use of my invention, I will proceed to a description of the same.

In the accompanying drawings, Figure l` represents a side elevation of a horizontal steam-engine with the cylinder and steamchest in section, showing the arrangements of the separate exhaust-valves in cavities between the steam-chest and cylinder, and the valve-gear Workingall the valves separate and independent of each other, operated by a single eccentric, suppressing consequently the steam at a Xed point of the stroke. Fig. 2 represents a top view of the eccentric-strap, showing the manner of attaching two rods to the same. Fig. 3 is a diagram explanatoryto the movements of the valve-gear as represented in Fig. 1. Fig. 4 is a di'agramexplan# atory of the movements of the 'valve-gear,

where said movements are derived from a link, so as to be able to suppress the steam at any desired point of the stroke.

Similar letters of reference denote the same parts in all the figures.

A is the cylinder; B, the piston; C, the steamchest; F F, the steam-valves on one end of the cylinder, and F' F the steam-valves on the other end of the cylinder. These steam-valves work on suitable seats, G and'G, in the bottom of the valve-chest and perform only the single office of admitting the steam. In the bottom of the valvechest C cavities P and P' are made,in which the exhaust-Valves H and H are situated, sliding on the surfaces J and J' on the cylinder A. On each end of the cylinder two openings, M N and M N', are made, the openings M M' forming passages between the ends of the cylinder through the recesses or cavities l? and P' in the bottom of the valve-chest, and the passages m in and m m', respectively, in the valve-seats G and G' in the steam-chest C, while the openings N and N' commu nicatc with the exhaust-port K, opening tothe condenser or atmosphere. These exhaust-valves perform only the single oflice of releasing the steam, andare formed similar to the usual cup-valves, and are'counected to a Valve-rod, w, passing through the exhaust passage or port K, and through suitable bosses through the ports M and M', and receive through said rod w a motion independent from the motion of the steam-valves, as will be hereinafter described. By this arrangement any amount of cut-ofi` may be given to the steam-valves, and at the same time the correct exhaust action will under all circumstances be maintained. rlhe steam-valves F F are connected to the valve-rod g,and the steamvalves F F are connected to the valve-rod g', and receive through said rods, which are connected to separate levers in the valve gear, as will be hereinafter mentioned, independent motions from each other.

E is the eccentric secured tothe crank-shaft L, so as to cut oli the steam at the desired point of the stroke.

D is the eccentric-strap, to which two eccentric-rods, O and Q, are attached, connected to separate arms B and S, respectively. These arms R and S are secured on independent rock-shafts, one of which passes through the other, so as to have a common center.

On the end of the shaft on which the arm B is fast another arm, R', is fastened, communicating, through the rod O', connected with the rod g, motion to the valves F F on one end of the cylinder, and on the end of the shaft on which the arm S is fast a crank, S', is fastened, communicating, throughthe rod Q', connected with the valve-rod g', motion to the steam-valves F' F' on the other end of the cylinder.

The positions of the arms R and S relatively to their respective arms R' and S are such that said arms B' and. S operate the steam-valves for the purpose of opening or closing the ports while the same travel a part of an arc having, relatively to the length of are passed over, a very large versed sine, and act upon said valves after the ports have been closed while traveling through a part of an arc where the versed sine diminishes while the distance of the are traveled through by the arm increases, and consequent-ly only very little motion is derived in proportion to the amount of travel of the arm or lever. rlhis accelerated motion to one or more valves, while opening or closing the port on one end ofthe cylinder, at the same time the valves covering the port on the other end of the cylinder receveavery slow motion, while being both derived from one and the same single eccentric, we obtain from the arrangement of the arms R'S',work ing independent of each other on the opposite sides ofthe center line, X X.

In Fig. 1 the piston B is represented at its bottom stroke, and the valves F F, communieating with the passages m m, leading to the bottom of the piston, just about to open.

By reference to the diagram,- Fig. 3, it will be perceived that the eccentric stands at thepoint marked l on the shaft, while the crank or arm R', to which the valves F F are connected, stands at the point marked 1 below the centerline,X X',which represents theline passing through the-center of motion of the roekshafts, and through the center line of the slide` valve rods, and in which position the valves F F are just ready to open the ports. Vh en the eccentric moves to point 2 around the shaft, the crank B' travels to point 2 on its circle,open` ing thereby the ports m m to their greatest extent in the short travel through the are from 1 to 2, and closes the same quite as fast while the eccentric travels from 2 to 3 around the shaft, at which latter position the arm R' is moved back again to point 1 in its arc and has closed the ports again. During the time the eccentric completes the revolution around the shaft from point 3 until it arrives again at point 1 the arm R is caused to move in its arc from 1 to 5 and back again to 1, traveling through an arc near the center line, X X', and may even pass said line a short distance, as shown in Fig. 4, consequently communicating only very little and a very'slow lnotion during all that time to the valves F F. Vhen the eccentric has arrived at point 4 around the shaft, the piston has traveled through the length of the cylinder, and has arrived at the t'op end of the same, or nearly so. The eccentric, which, as above described, has operated, through its rod O, the arm R, with which the arm B' is connected, so that the latter'has moved the valves F F over the ports on m, operates likewise, through the rod Q, the arm S, to which the arm S' is connected, and has brought, when arrived at point 4 around the shaft, said arm S to the point 4 in its circle above the center line, XX', in which position the valves F F at the top end of the cylinder are on the point of opening the ports m' m' for the admission of the steam in the top end of the cylinder. When the eccentric arrives at point 5 on the shaft, the arm S has moved to point 5 on its circle and opens full the ports m m. and when the eccentric arrives at point 6 ou the shaft the arm S is moved back againl to point 4 on its arc and the valves F F have closed again the ports m m. During the time the eccentric travels around the shaft from point 6 until it arrives again at point 4, and while said eccentric operates through its rod O, the arms R and R', and through the latter the valves F F, as above described, the rod Q of saideccentrc acts upon the arm S so as t0 cause the arm S to move in the arc from 4 to 2, near the center line, X X', and back again, keeping during that time the valves F F over the ports n1, m, and communicating only very little anda very slow motion to the same. On either of the rock-shafts an armor lever is attached, connected, through the rod U,with the valve-rod w, to which the exhaust-valves H and H are fastened, as above described. This arm is placed in such a position as to work the exhaust-valves n the usual manner.

The exhaust-valves (as here represented) are both connected to one rod, w, in which case the same can be operated by one arm placed on either of the rock-shafts; but when said valves are separated and attached to separate rods they must be operated by separate arms placed on each of the rock-shafts.

The exhaust-valve H on one end of the .cylinder may be connected With the steam-valves F F onA the opposite end of the cylinder, and the exhaust-valve H at the bottom end of the cylinder connected with the steam-valves F F' at the top end of the cylinder, in which case the same motion communicated to the steam-valves will be communicated to the respective exhaust-valves without any separate arms being required on either or on bot-h the rock-shafts for working said exhaust-valves.

ltheir respective steam-valves, in the manner substantially as above specified. The exhaustvalves derive in this case their motion from a pin, p, fixed in the solid part of the link,connccted through thel rod V with an arm, T. Another arm, T', attached to the same rockshaft to which the arm T is fastened, communicates the required motion to the exhaustvalves, by which arrangement any amount of cut-off given to the steam-valves will not interfere with the correct action of the exhaustvalves.

Instead of the above-described arrangement of a split eccentric-rod or two eccentric-rods l to one eccentric-strap, au equivalent construction will be two eccentrics set in the same position on the shaft,with theirusual straps and rods, or two straps placed upon one and the same eccentric, with rods to each strap and each rod attached to a separate crank.

Having thus described my invention and fully set forth the manner oi" putting the same into practice, I claimi The herein-described arrangement of valves worked by means of separate rods and levers operated from the action of a single eccentric, the whole being combined and operated in the manner and for the purpose substantially as set forth.

JOHN F. ALLEN. Vitnesses:

HENRY E. ROEDER, GHARLEs S. BENNETT. 

